Thread: Always player #1's turn?

After reviewing the below code for the past hour, I cannot seem to figure out this problem.

This is a basic WIP for a tic-tac-toe game (I'm new to C and thought this would be a decent little challenge). I've got most of everything done, however - after you enter in Player #1's name and Player #2's name, the program will ALWAYS give the turn to whoever was assigned as Player #1 (who is assigned as player #1 is supposed to be random).

So, to summarize:

>enter in player #1's name [josh]
>enter in player #2's name [justin]
>program randomly assigns josh as player #1
>[turn #1] josh, make your move
>enter in coordinates
>[turn #2] josh, make your move

It never gives a turn to player two. Any ideas why this is? Thanks.

Code:

#include <stdio.h>
#include <string.h>
#include "player.h"


int board[3][3];
int maxInput = 3; /* this represents the maximum int they can specify when choosing a position to play */
int a = 0; //represent the turn currently being played
int done = 0;


struct players player[2];


//prototypes
int isEven(int x);
void markPosition(int x, int y, char type);
void checkForWinner();


int main()
{
    int first; //the player the goes first


    int x;
    int y;


    printf("Player one, enter your name: ");
    fgets(player[0].name, 256, stdin);


    printf("Player two, enter your name: ");
    fgets(player[1].name, 256, stdin);


    //remove \n at the end of each name
    player[0].name[strlen(player[0].name)-1] = '\0';
    player[1].name[strlen(player[1].name)-1] = '\0';


    //generate who will go first randomly
    first = (isEven(rand())) ? 1 : 0;


    //set who is x, who is y
    if(first == 1){
        player[0].type = 'O';
        player[1].type = 'X';
    }else{
        player[0].type = 'X';
        player[1].type = 'O';
    }


    printf("Player %s, you are X.\n", player[first].name);
    printf("=========================\n");


    while(done == 0){
        a++;
        printf("\n\n[TURN %d] %s, make your move.", a, (isEven(a) && first == 1) ? player[1].name : player[0].name);


        printf("\nInput X-Coord: ");
        scanf("%d", &x);


        printf("\nInput Y-Coord: ");
        scanf("%d", &y);


        markPosition(x,y, (isEven(a) && first == 1) ? player[1].type : player[0].type);
        checkForWinner();
    }


    FILE *file;
    file = fopen("C:\\Users\\Justin\\Desktop\\tictactoe_results.txt", "w+");


    //print results of the board/game into a text file
    int o = 0;
    int z = 0;
    int b;
    for(b = 0; b < 9; b++){
        //if the position isn't played, set it to the char -, else write who played that pos
        fputc((board[o][z] == NULL) ? '-' : board[o][z], file);


        if(o == 2) fputc('\n', file);


        if(o >= 2){
            o = 0;
            z++;
        }else{
            o++;
        }
    }


    fclose(file);
    getchar();
}


int isEven(int x){
    return !(x%2);
}


void checkForWinner(){
    if(a == 9){
        done = 1;
    }
}


void markPosition(int x, int y, char type){
    if(board[x][y] != NULL){
        printf("[ERROR] You cant select position already played.\n");
        if(a > 0) a--;
    }else if(x > maxInput || y > maxInput){
        printf("[ERROR] Your coordinates are off the board! \n");
        if(a > 0) a--;
    }else{
        board[x][y] = type;
    }
}

You could give each player a number, say 0 or 1

then, right before you loop back to the top of the game loop:

Code:

player = !player;

An example:

Code:

#include <stdio.h>

int main(void) {
   volatile int i, player;
   i=player=0;
   while(i<5) {
      printf("Player is: %d \n",player);
      player=!player;
      ++i;
   }
   return 0;
}

Originally Posted by Salem

There was no need to make that volatile Adak.

Oh yes there was!

AVG free edition's latest upgrade, prevents it from running, if the volatile keyword is removed. Declaring it a virus!

I tried making subtle changes to the code itself, like using an if() statement, etc., but that didn't work.

Adding volatile was the only thing that let it get past AVG.

I'm hoping the next update in a few days, will have that false positive problem, fixed.

Originally Posted by Salem

Why would anyone else here care about your virus scanner issues - or your inability to configure it?

You asked, so I answered. Why do you think I can't configure it? There never was a reason to exclude a directory with the previous versions of AVG.

Why would anyone else here, care about anything? Because we're all human. Some more pleasant than others.

Originally Posted by Salem

> printf("\n\n[TURN %d] %s, make your move.", a, (isEven(a) && first == 1) ? player[1].name : player[0].name);

Originally Posted by Salem

Well if first is 0, then first == 1 will always be false.
Which makes the && expression itself always false, the isEven(a) plays no further part.

Ah, I guess that slipped away from me and I never really caught that.

Thanks for the reply.

Originally Posted by Adak

You could give each player a number, say 0 or 1

then, right before you loop back to the top of the game loop:

Code:

player = !player;

An example:

Code:

#include <stdio.h>

int main(void) {
   volatile int i, player;
   i=player=0;
   while(i<5) {
      printf("Player is: %d \n",player);
      player=!player;
      ++i;
   }
   return 0;
}

Thank you for the provided concept!

Worked perfectly.